To split a column into two you have to use a CASE function as shown in the example.
The SUBSTRING used in the example is used to get rid of the negative sign infront of the number
so that there are only positive numbers in the table.

To combine two columns into a single one you also use a CASE function to do this with this example you can use this code:

SELECT w AS dte, d AS description,
CASE WHEN (a>=0)
THEN a ELSE NULL END AS amount,
CASE WHEN (b>=0)
THEN b ELSE NULL END AS amount
FROM
(SELECT x.whn AS w, x.description AS d,
x.cshIN AS a, x.cshOUT AS b
FROM transact x
JOIN transact y ON (x.whn>=y.whn)
GROUP BY x.whn, x.description, x.amount) t